Slot Antenna Ultrasonic Proximity Sensing for SAR Mitigation
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Solution Overview
Problem
Current proximity sensing techniques for electronic devices impose design constraints and increase near-field emissions, leading to higher energy absorption by human tissue and stricter SAR compliance requirements, particularly in smaller devices.
Innovation Solution
Implementing ultrasonic proximity sensing using a slot antenna with an integrated acoustic transceiver that transmits and receives ultrasonic waves through a slot in the device's metal exterior, allowing for accurate distance calculation and adjustment of transmission power to comply with SAR standards without shielding antenna emissions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If traditional capacitive proximity sensing is used, then proximity detection is achieved, but antenna emissions are shielded and near-field emissions increase
Solution Approach 1:
The patent replaces the traditional capacitive sensing system with an ultrasonic acoustic wave system. Instead of using electromagnetic fields for proximity detection, the invention uses acoustic waves that mechanically vibrate to detect proximity. This substitution eliminates the shielding effect on RF antenna emissions while maintaining accurate proximity detection capability through temporal separation between acoustic wave transmission and RF signal transmission.
2Volume of moving object
If device size is reduced, then portability is improved, but SAR compliance becomes more difficult to achieve
Solution Approach 1:
By replacing capacitive sensing with ultrasonic sensing, the system enables smaller device form factors without compromising SAR compliance. The ultrasonic acoustic waves do not interfere with RF antenna radiation patterns, allowing compact antenna designs while maintaining accurate proximity detection for SAR mitigation.
Solution Approach 2:
The system uses periodic ultrasonic acoustic wave transmission followed by echo reception to continuously monitor proximity. This periodic acoustic sensing enables real-time SAR compliance adjustment in small devices, allowing the antenna to operate at full power when no object is detected and reduce power when proximity is detected, thus maintaining SAR standards in compact form factors.
3Power
If transmission power is increased, then communication performance is improved, but SAR compliance is violated when objects are nearby
Solution Approach 1:
The ultrasonic proximity sensing system provides continuous feedback about object proximity to the transmission power control mechanism. When acoustic wave echoes indicate an object is within the SAR-sensitive zone, the system automatically reduces transmission power. When no object is detected, the system operates at maximum power, thus optimizing communication performance while ensuring SAR compliance through real-time feedback-based power adjustment.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
Ultrasonic proximity sensing provides a compact and accurate method to determine object proximity, reducing unnecessary transmission power and maintaining SAR compliance, while minimizing design constraints and shielding issues.
Implementation Method 1
An acoustic transceiver is positioned within the computing device to transmit an acoustic wave out through the slot
Implementation Method 2
to receive a reflected portion of the acoustic wave in through the slot when the acoustic wave is reflected by a nearby object
Implementation Method 3
determines a physical separation between the object and the slot antenna based on a temporal separation between transmission of the acoustic wave and receipt of the reflected portion of the acoustic wave
Data Source
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AI summary
The disclosed technology provides a computing device with a slot antenna assembly including a slot formed in a metal exterior surface of a computing device case; an acoustic transceiver positioned to transmit an acoustic wave out through the slot and to receive a reflected portion of the acoustic wave in through the slot when the acoustic wave is reflected by an object; a proximity detector coupled to the acoustic transceiver that determines a physical separation between the object and the slot antenna based on a temporal separation between transmission of the acoustic wave and receipt of the reflected portion of the acoustic wave; and a transmission power controller that adjusts transmission power of the slot antenna based on the determined physical separation.